Aircraft: SAIL PLANE
Phase of flight: Takeoff / Launch
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy

After a break for lunch from morning towing we returned to the airport and listened to the weather on AWOS. I commented that the time on AWOS was 3 minutes fast. Winds were SW at 8 knots. The others prepped aircraft for launch and towing. We towed the plane from the tie down area on the ramp to about the 1500 ft mark on the west side of the runway; crossing the grass between the runway and taxiway. We parked the glider outside of the line of the runway lights. I sat in the forward cockpit; fastened my seat harness; checked the controls; and made sure the spoilers were locked by pushing forward on the spoiler control while the tow-out gear was removed. Before the instructor entered the cockpit; he checked to make sure my harness was fastened. After the instructor was seated; he indicated that since this was my first winch launch; the flight would be to familiarize me with a winch launch; that he would do the flying; and that I was welcome to follow along on the controls. He also covered the sensations that I would feel during the launch. I adjusted my headrest to insure that my head would not tilt back. I checked with the instructor and turned on the master. We set the altimeters to field elevation and listened to the radio to follow local traffic while waiting for the tow line. We also talked about trim position and confirmed the position of the trim. I spent some time trying to get the S80 to turn on; although I was not successful. I do not specifically remember what else we discussed nor what else was done while waiting.After the tow line was attached the instructor made a radio call that we were taking the runway. We were pulled onto the runway. I operated the release and commented on how much farther I had to pull compared to the nose release. At this point we closed the canopies. I checked to make sure that the canopy pin was protruding from the front of the latch and again pushed forward on the spoilers to make sure that the spoilers were locked. I called out that my canopy was closed and locked and that spoilers were closed and locked. The instructor also called out canopy closed and locked and spoilers closed and locked and I saw the control stick move around its full range of travel. Upon the instructor's signals; the strop was attached to the tow line; we checked for traffic; and leveled the wings. I placed my right hand lightly on the stick; my feet lightly on the rudder pedals; and my left hand on my left leg. The instructor called on the radio 'slack; slack; slack'; and called out 'rope alive'. When the glider moved forward slightly; the instructor called on the radio 'go; go; go' and the glider accelerated forward. Somewhere during the process of getting ready on the runway; the instructor made a two-minute radio call and a launch radio call; but I do not remember where they were in the sequence.I remember a tremendous acceleration and the airspeed coming alive. We rotated and began a rapid climb. Airspeed and pitch were steady throughout the tow. Suddenly there was a rapid change in cockpit pressure. I saw the spoiler handle move aft; and there was a lot of dust moving around the cockpit. I looked out the left to confirm the spoiler was extended and it was. At this point I heard the instructor yell 'take the airplane' and I took control and yelled 'I have the airplane'. He apparently did not hear me and he again yelled 'take the airplane' as I was lowering the nose and closing the spoilers. So I yelled as loud as I could 'I have the plane'. I looked out the right side to make sure that the spoilers had closed and this is when I noticed that the rear canopy was slightly open. I got a glimpse of the rear canopy frame extending slightly past the glider cockpit frame. I do not remember the noise and I also do not remember the release from the tow line. I stabilized the glider; noticed the altimeter about 6800'and gingerly tried the controls. Everything was working fine and the glider was behaving normally. I could not see any damage. The instructor told me that the canopy had opened and was broken but intact. He also indicated that I should land the glider. I slowly accelerated to 70 MPH and retrimmed the glider. I made a shallow left turn and entered a high left downwind. I continued a normal approach; went through the landing checklist; landed on runway and stopped next to a taxiway. As we exited the glider; I noticed that the rear canopy was cracked with a circular piece missing on the right side. The eyebolt that holds the limit cord was also broken. The instructor had a cut on his right wrist and he indicated that his shoulder was sore. We pushed the glider back to the ramp. A glider crew experienced a rear canopy malfunction resulting in a partially open rear canopy. Front-seat pilot landed the glider.